Incidence and Risk Factors for Acquisition of Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae in Newborns in Seville, Spain: A Prospective Cohort Study

ABSTRACT Background ESBL-producing Enterobacteriaceae (ESBL-E) are an emerging cause of infections in children. Data are scarce on incidence rates and risk factors for acquisition of colonisation with ESBL-E. Methods A total of 46 and 50 newborns from colonised and non-colonised mothers, respectively, were followed during one year after birth. Rectal swabs were performed every 3 months to detect ESBL-E; bla ESBL were characterised and isolates were typed for comparison. Multivariate analysis for risk factors was performed using Cox regression. Results Incidence density of any new acquisition and of first acquisition of ESBL-E was 2.7 and 1.9 episodes per 100 children-month, respectively, among children whose mothers were colonised, and 1.2 and 1.3, respectively, among children whose mothers were not. The weighted average prevalence of colonisation rates during the first year were 15.9% and 8%, respectively. No infections due to ESBL-E were detected. Living with pets at home, breastfeeding, sterilisation of feeding bottles and out-of-home childcare were protective for ESBL-E acquisition; having a colonised mother increased the risk. The most frequent ESBL types were CTX-M-14 and CTX-M-1. In 5/19 (26.3%) children with acquisition of new clones, the acquired ESBL-E was shared with their mothers. Conclusions Acquisition of ESBL-E colonisation is not rare during the first year of life. Breastfeeding and out-of-home childcare were protective for acquisition, and colonised mothers were associated with increased risk. However, the same clone was shared by mother and child in only a subset of acquisition episodes.